The role of the Kallikrein system in adaptation to acute alteration in extracellular volume and salt concentrations was evaluated in female Sprague-Dawley rats. Extra-cellular volume was expanded by 20% with either NS or D5W over a period of one hour, at which point the infusion was either stopped or continued to match urine output. There was no correlation between kallikrein and urinary volume, sodium, or potassium. Kallikrein excretion demonstrated a pattern suggestive of a tubular "washout" phenomenon in response to volume expansion that was unaffected by adrenalectomy.